Pseudomonas aeruginosa produces a variety of extracellular products which may play a significant role in the pathogenesis of Pseudomonas infections in experimental animal models and in humans. Two of these factors, exotoxin A and protease(s), are likely candidates to be major virulence factors of P. aeruginosa; however, the role and interaction of these factors in the pathogenesis of Pseudomonas infections has not yet been clarified. The ultimate objective of this research is to employ genetical techniques complemented with other experimental methods to obtain valuable information concerning the role of exotoxin A and proteases as virulence factors of P. aeruginosa. As further insight into the role of specific virulence factors in the pathogenesis of Psuedomonas infections is gained, it is likely that the principles of genetics, including genetic engineering, can be applied to the practical problems of developing prophylactic and therapeutic agents for patients with Pseudomonas infections. Immediate objectives are: (1) to elucidate the genetic mechanisms which regulate the production of exotoxin A and proteases. The well characterized conjugal mating system of P. aeruginosa will be used to further map and analyze genetic determinants controlling toxin production and production of proteases. The transducing system of P. aeruginosa will be potentially useful for fine structure mapping of the tox gene(s) and to determine the role if any that bacteriophage play in the production of exotoxin A or proteases. (2) To isolate and fully characterize spontaneous or chemically induced mutants of P. aeruginosa with altered ability to produce exotoxin A and/or proteases. Mutants will be subjected to further extensive biochemical and genetical analyses. (3) To examine and compare the virulence of mutants and wild type strains in appropriate experimental animal models. Ultimately, preliminary studies could be conducted with experimental animals to determine if a mutant strain or a CRM toxin has the potential to be an effective immunoprophylactic agent against Pseudomononas infections.